This invention relates to apparatus for sealing pavement joints or seams in general and in particular to apparatus for sealing pavement seams which do not require the utilization of sealing materials which must be heated to predetermined temperatures to achieve molten states. Still more particularly, this invention relates to sealing compositions for use in such devices which have enhanced operating characteristics.
It is well known in the prior art that when large expanses of concrete are poured and allowed to harden over a relatively dynamic base, such as clay soil, subsequent movement of that base will result in fractures and cracks in the concrete. These fractures and cracks are due to temperature and moisture gradients which exist in the concrete due to the differences between the temperature and moisture content of the top and the bottom of a pavement slab and to shrinkage which occurs during curing. In an effort to direct such fractures and cracks along less damaging lines, it has become common practice to produce seams in such concrete expanses by cutting or sawing the concrete after hardening, or by utilizing some flexible material which is embedded in the concrete while it is in a plastic state. The utilization of sawed or cut seams is most prevalent in this area, particularly in applications such as parking lots and streets or highways.
It has also become known in the art that some form of flexible sealant must be inserted into such seams to stem the increased flow of surface water into the base beneath these seams. The sealant utilized must be capable of standing repeated expansion and contraction as the pavement expands and contracts with temperature and moisture changes. This is particularly important in areas where the soil contains a high clay content as the surface water which flows through such seams will result in a significant expansion of the subsurface soils and have a particularly deletorious effect of the stability of the concrete. Thus, it has become necessary to seal these concrete seams with a waterproof material to prevent damage to the concrete structure. Further, the sealant material must preferably be contained entirely within the seam or gap to prevent its removal if it adheres to the tires of vehicles passing over the seam.
Prior art solutions to this problem have consisted almost entirely of expensive and difficult to install plastic materials or heated asphaltic materials which are difficult and dangerous to utilize. Numerous examples of devices which utilize asphaltic materials and an accompanying heating device abound in the art. The difficulty in utilizing a heated mass of asphalt and accurately applying such materials into a narrow gap has generally been well recognized; however, no acceptable alternative has been proposed. Thus, while this technique is quite dangerous, it has remained the primary method of sealing pavement seams.
Recently, certain asphaltic emulsion sealing materials have been proposed for utilization in the sealing of pavement seams; however, these materials suffer from several serious drawbacks. Many of these materials harden when exposed to air and this makes it quite difficult to apply them into a pavement seam without premature curing. Additionally, many of the emulsion materials suffer from premature breakdown or lumping during utilization and this therefore renders the application of these materials to a narrow pavement seam quite difficult.